Step 1

Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and line a 23cm x 33cm swiss roll tin with baking paper

Step 2

Melt the dark chocolate in a glass bowl over water, or in the microwave. If melting in the microwave make sure to use a microwave safe bowl, start with a 30 second blast, stir the chocolate, then continue with 10 second blasts stirring in between until melted

Step 3

Whisk up the yolks of the eggs and the caster sugar until thick and creamy

Step 4

Use an electric food mixer or electric hand whisk to whisk up the whites from the eggs until stiff peaks form - you will know they are done when you can tip the bowl upside down and the whites do not move

Step 5

Whisk the melted chocolate into the egg yolk mixture

Step 6

Fold in half of the egg whites, then add the rest and fold in gently

Step 7

Finally fold in the sieved cocoa powder

Step 8

Pour the mixture into the baking tray and spread it out evenly with a palette knife or silicone spatula. Bake for 20 minutes then leave to cool in the tin

Step 9

Whip up the double cream with the icing sugar and the Baileys

Step 10

Tip the sponge out onto a piece of baking paper dusted with icing sugar and spread the cream over it, leave about a 2cm space at one end of the sponge

Step 11

Gently roll the sponge up starting with the cream filled end, don't worry if it cracks a little bit as it is supposed to. Trim the ends with a serrated knife for a neater finish. Dust it with more icing sugar if you like

Step 12

Serve immediately, store leftovers in the fridge and eat within 2 days